This is the 268th most frequent Vietnamese word.
nổi
"To float," "to arise," or "to emerge."
Here, 'nổi' refers to the bubbling action happening due to boiling, emphasizing its upwards movement.
Nước sôi này đã nổi bong bóng khắp bề mặt.
This boiling water has bubbles all over its surface.
In this context, 'nổi' is used to describe an emotion rising or emerging, akin to flaring up.
Cô ấy nổi giận rất nhanh trong tình huống này.
She quickly got angry in this situation.
Here, 'nổi' forms part of the phrase 'nổi bật', meaning 'to stand out', used metaphorically to describe being noticeable.